1. Technical Field
The present invention relates in general to a system and method for swapping Radio Frequency Identification (RFID) tag data read at portals, such as dock doors. In particular, the present invention relates to a system and method to manage cross reads without use of physical shielding traditionally used to isolate RFID readers from one another.
2. Description of the Related Art
Radio Frequency Identifiers (RFID) is a means of identifying a unique object that has been tagged with a physical RFID tag by using a radio frequency transmission. Data stored in the RFID tags (also called transponders) is wirelessly transmitted to readers (also called interrogators) in an automated fashion. RFID readers can be stationary or portable, such as handheld readers. One example of a stationary reader is a reader that is installed proximate to loading dock doors to read tags from objects being moved through the dock doors.
RFID tags are affixed to objects. Each RFID tag includes an embedded microchip where information about the object is stored. RFID tags are typically powered by a radio frequency signal sent by the RFID reader. In response to receiving the radio frequency signal, the RFID tag responds by transmitting the identification data stored on the RFID tag. The radio frequency signals received by the RFID tags may be sent over a range of distances. When many objects are in proximity to a RFID reader, each of the RFID tags that receives the radio frequency signal responds by transmitting the data encoded on the RFID tag.
For example, assume 1,000 RFID-tagged objects are in proximity to an RFID reader that sends a radio frequency signal. Because of positioning of the objects, only 500 of the RFID-tagged objects receive the radio frequency signal, then these 500 RFID tags would transmit identification data back to the RFID reader. Each time the RFID reader sends the radio frequency signal, all of the RFID tags that receives the signal responds by transmitting the RFID data irregardless of whether the RFID tags have already been read. Assume that, in our example, the objects are being moved past the reader that periodically sends out the radio frequency signal. As objects are repositioned, some tags that did not originally receive the signal now receive the signal due to their new position in proximity to the RFID reader. Some objects, such as metal or aluminum cans filled with liquid (e.g., soda cans), may act as an insulator that prevents some of the RFID tags from receiving the radio frequency signal even while when the objects are moved. Other tags may not be able to be read because they are surrounded by too many other objects, such as a tag in the middle of a pallet.
As used herein, a pallet is a portable container, or platform, used for storing and moving objects, such as cargo or freight. Pallets are often used to store and move case goods. The cases and other objects stored on an individual pallet may be all of the same type (e.g., a pallet that only has boxes (cases) of oranges) or may have cases or objects of different types (e.g., a pallet that has some cases of oranges, some cases of apples, etc.). A pallet identifier is an RFID tag that uniquely identifies a particular pallet of goods. Each of the cases or objects included in the pallet is also uniquely identified. Using the examples from above, in the first example, a unique pallet identifier would be affixed somewhere on the pallet and each of the cases of oranges would also have RFID tags that uniquely identify each of the cases. Likewise, in the mixed-case example, a unique pallet identifier would be affixed somewhere on the pallet and each of the cases of oranges, apples, etc., would also have RFID tags affixed that uniquely identify the various objects (cases) included in the pallet.
In modern distribution settings, when goods are shipped the distributor (shipper) sends an electronic manifest to the customer (receiver). The electronic manifest details the pallet identifiers as well as the case level identifiers. When the customer receives the shipment, the customer's RFID readers read the tags on the pallets and cases and compares the tags that were read with the data included in the electronic manifest.
A challenge encountered when receiving goods by a receiver that has more than one RFID reader is cross reads. A cross read occurs when one RFID reader sends a radio frequency signal to read the RFID tags and receives additional RFID tag information for RFID tags that are being processed by a different RFID reader. For example, a receiver may have multiple dock doors for receiving goods offloaded by semi-trucks, freight trains, or other cargo transporters. When an RFID reader installed at one dock door sends the radio frequency signal, RFID tags affixed to goods that are arriving at a different dock door (and, thus, a different RFID reader) will also transmit their data if they receive the radio frequency signal. This is especially problematic when RFID readers are close to one another, such as those at adjacent dock doors. One approach to this challenge is to install shielding, typically metal, to isolate RFID readers from each other. One problem with this approach is that such shielding is often large and expensive. Another problem is that some cross-reads may still occur based on the proximity of the goods in relation to the RFID reader.
What is needed, therefore, is a system and method that identifies RFID tags destined for another RFID reader without the need for physically shielding the RFID readers from one another. Furthermore, what is needed is a system and method where data read at one RFID reader is transmitted to other RFID readers.